Predefined Constants Reference

I'm new to Arduino, and am learning by a sort of osmosis that there are many useful constants pre-defined in the Arduino core. However I have not been able to find a comprehensive listing or reference to them. If I've missed it I'll be very happy for a pointer!

A master reference to all pre-defined constants may need to bridge libraries and could be a PITA to maintain, but it would seem to be a VERY useful reference. Things like timer registers, pin definitions... true/false - whatever - there should be a master, printable reference PDF somewhere - if there isn't already!

=Alan R.

Welcome in Ardunioland,

You should check the installation of the Arduino

  • C:\Program Files (x86)\arduino-0022\hardware\arduino\cores\arduino -
  • C:\Program Files (x86)\arduino-0022\libraries -

and check the underlying .h files.

For newer versions or other os the path is more or less (or far more) different of course.

Things like timer registers, pin definitions... true/false - whatever - there should be a master, printable reference PDF somewhere

Well, all the Atmel-defined symbols (timer registers, for instance) should get defined via the <io.h> include that is part of gcc. The chip datasheet is probably the reference for those. The m328 has about 100 registers, each of which has individual names for most of its individual bits (because you know PORTA4 might somehow have a different value than PORTB4), so a full listing is probably going to be too cluttered to be useful.

arduino.h is going to have most of the arduino-specific values; there are a lot less of those.

Solution Found! :grin:

I simply got a PDF of the Atmel ATmega/xxx/328P datasheet (a mere 450 some pages!) and, while not in an particular order, I think every constant in the Arduino world can be found there. Makes for some (dry) but enlightening reading!

Now - if you think 450 pages is big, you should checkout the datasheet (more like "data-WarandPeace" for the chip in the DUE - the Cortex ARM SAM3X... that puppy weights in at 1467 pages!

=Alan R.

Harrzack:
Solution Found! :grin:

I simply got a PDF of the Atmel ATmega/xxx/328P datasheet (a mere 450 some pages!) and, while not in an particular order, I think every constant in the Arduino world can be found there. Makes for some (dry) but enlightening reading!

Now - if you think 450 pages is big, you should checkout the datasheet (more like "data-WarandPeace" for the chip in the DUE - the Cortex ARM SAM3X... that puppy weights in at 1467 pages!

=Alan R.

Actually no, you found none of the Arduino constants, but rather you found AVR constants.

The IDE core file Arduino.h contains the majority of the Arduino defines, constants, and macros, which in turn also includes several other files with most (all?) the avr defines, constants, and macros used by the arduino IDE:

#ifndef Arduino_h
#define Arduino_h

#include <stdlib.h>
#include <string.h>
#include <math.h>

#include <avr/pgmspace.h>
#include <avr/io.h>
#include <avr/interrupt.h>

#include "binary.h"

#ifdef __cplusplus
extern "C"{
#endif

#define HIGH 0x1
#define LOW  0x0

#define INPUT 0x0
#define OUTPUT 0x1
#define INPUT_PULLUP 0x2

#define true 0x1
#define false 0x0

#define PI 3.1415926535897932384626433832795
#define HALF_PI 1.5707963267948966192313216916398
#define TWO_PI 6.283185307179586476925286766559
#define DEG_TO_RAD 0.017453292519943295769236907684886
#define RAD_TO_DEG 57.295779513082320876798154814105

#define SERIAL  0x0
#define DISPLAY 0x1

#define LSBFIRST 0
#define MSBFIRST 1

#define CHANGE 1
#define FALLING 2
#define RISING 3

#if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__) || defined(__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
#define DEFAULT 0
#define EXTERNAL 1
#define INTERNAL 2
#else  
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega644P__)
#define INTERNAL1V1 2
#define INTERNAL2V56 3
#else
#define INTERNAL 3
#endif
#define DEFAULT 1
#define EXTERNAL 0
#endif

// undefine stdlib's abs if encountered
#ifdef abs
#undef abs
#endif

#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))
#define abs(x) ((x)>0?(x):-(x))
#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
#define round(x)     ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))
#define radians(deg) ((deg)*DEG_TO_RAD)
#define degrees(rad) ((rad)*RAD_TO_DEG)
#define sq(x) ((x)*(x))

#define interrupts() sei()
#define noInterrupts() cli()

#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
#define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() )
#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() )

#define lowByte(w) ((uint8_t) ((w) & 0xff))
#define highByte(w) ((uint8_t) ((w) >> 8))

#define bitRead(value, bit) (((value) >> (bit)) & 0x01)
#define bitSet(value, bit) ((value) |= (1UL << (bit)))
#define bitClear(value, bit) ((value) &= ~(1UL << (bit)))
#define bitWrite(value, bit, bitvalue) (bitvalue ? bitSet(value, bit) : bitClear(value, bit))


typedef unsigned int word;

#define bit(b) (1UL << (b))

typedef uint8_t boolean;
typedef uint8_t byte;

void init(void);

void pinMode(uint8_t, uint8_t);
void digitalWrite(uint8_t, uint8_t);
int digitalRead(uint8_t);
int analogRead(uint8_t);
void analogReference(uint8_t mode);
void analogWrite(uint8_t, int);

unsigned long millis(void);
unsigned long micros(void);
void delay(unsigned long);
void delayMicroseconds(unsigned int us);
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout);

void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val);
uint8_t shiftIn(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder);

void attachInterrupt(uint8_t, void (*)(void), int mode);
void detachInterrupt(uint8_t);

void setup(void);
void loop(void);

// Get the bit location within the hardware port of the given virtual pin.
// This comes from the pins_*.c file for the active board configuration.

#define analogInPinToBit(P) (P)

// On the ATmega1280, the addresses of some of the port registers are
// greater than 255, so we can't store them in uint8_t's.
extern const uint16_t PROGMEM port_to_mode_PGM[];
extern const uint16_t PROGMEM port_to_input_PGM[];
extern const uint16_t PROGMEM port_to_output_PGM[];

extern const uint8_t PROGMEM digital_pin_to_port_PGM[];
// extern const uint8_t PROGMEM digital_pin_to_bit_PGM[];
extern const uint8_t PROGMEM digital_pin_to_bit_mask_PGM[];
extern const uint8_t PROGMEM digital_pin_to_timer_PGM[];

// Get the bit location within the hardware port of the given virtual pin.
// This comes from the pins_*.c file for the active board configuration.
// 
// These perform slightly better as macros compared to inline functions
//
#define digitalPinToPort(P) ( pgm_read_byte( digital_pin_to_port_PGM + (P) ) )
#define digitalPinToBitMask(P) ( pgm_read_byte( digital_pin_to_bit_mask_PGM + (P) ) )
#define digitalPinToTimer(P) ( pgm_read_byte( digital_pin_to_timer_PGM + (P) ) )
#define analogInPinToBit(P) (P)
#define portOutputRegister(P) ( (volatile uint8_t *)( pgm_read_word( port_to_output_PGM + (P))) )
#define portInputRegister(P) ( (volatile uint8_t *)( pgm_read_word( port_to_input_PGM + (P))) )
#define portModeRegister(P) ( (volatile uint8_t *)( pgm_read_word( port_to_mode_PGM + (P))) )

#define NOT_A_PIN 0
#define NOT_A_PORT 0

#ifdef ARDUINO_MAIN
#define PA 1
#define PB 2
#define PC 3
#define PD 4
#define PE 5
#define PF 6
#define PG 7
#define PH 8
#define PJ 10
#define PK 11
#define PL 12
#endif

#define NOT_ON_TIMER 0
#define TIMER0A 1
#define TIMER0B 2
#define TIMER1A 3
#define TIMER1B 4
#define TIMER2  5
#define TIMER2A 6
#define TIMER2B 7

#define TIMER3A 8
#define TIMER3B 9
#define TIMER3C 10
#define TIMER4A 11
#define TIMER4B 12
#define TIMER4C 13
#define TIMER4D 14	
#define TIMER5A 15
#define TIMER5B 16
#define TIMER5C 17

#ifdef __cplusplus
} // extern "C"
#endif

#ifdef __cplusplus
#include "WCharacter.h"
#include "WString.h"
#include "HardwareSerial.h"

uint16_t makeWord(uint16_t w);
uint16_t makeWord(byte h, byte l);

#define word(...) makeWord(__VA_ARGS__)

unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);

void tone(uint8_t _pin, unsigned int frequency, unsigned long duration = 0);
void noTone(uint8_t _pin);

// WMath prototypes
long random(long);
long random(long, long);
void randomSeed(unsigned int);
long map(long, long, long, long, long);

#endif

#include "pins_arduino.h"

#endif

Lefty

Don't you think the PI related constants are a bit too long? I thought arduino only has single precision floating point numbers. Those numbers are too long even for double.

PI is prepared for the DUE :wink: